DISCLAIMER: This is a working document provided by the Centers for Disease Control and Prevention (CDC) 

technical support contractor, SC&A for use in discussions with the National Institute for Occupational Safety and 

Health (NIOSH) and the Advisory Board on Radiation and Worker Health (ABRWH), including its Working Groups or 

Subcommittees. Documents produced by SC&A, such as memorandum, white paper, draft or working documents are 

not final NIOSH or ABRWH products or positions, unless specifically marked as such. This document prepared by 

SC&A represents its preliminary evaluation on technical issues.

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

Memorandum

To: SEC Issues Work Group, Savannah River Site Work Group

From: SC&A, Inc.

Date: July 29, 2021

Subject: Application of NOCTS Data 2021

1.0 Introduction and Purpose

Some members of the Savannah River Site (SRS) and Special Exposure Cohort (SEC) Issues 

work groups have recently expressed interest in the representativeness of data from the National 

Institute for Occupational Safety and Health (NIOSH) DCAS Claims Tracking System (NOCTS) 

for use in co-exposure models. This concern was most recently broached during discussions by 

these work groups about ORAUT-RPRT-0094, “Bioassay for Subcontractor Construction Trade 

Workers at the Savannah River Site from 1972 to 1997” (NIOSH, 2019b), and the recent 

“bootstrap” pilot analysis for SRS (NIOSH, 2021a, 2021b) that exemplify NIOSH’s continued 

interest in making more use of its NOCTS dataset. With the lengthy history of this issue, it is

best to provide a brief chronology and summary of what SC&A believes are the key 

considerations; this memorandum is that summary, tasked in May 2021. 

2.0 SC&A Summary of Reports and Past Advisory Board Discussions of NOCTS 

Dataset Applications

SC&A believes that three main NIOSH documents are most germane to this discussion: 

ORAUT-OTIB-0075 (OTIB-0075), ORAUT-OTIB-0081 (OTIB-0081), and ORAUT-RPRT0094 (RPRT-0094), discussed in sections 2.1, 2.2, and 2.3 of this memorandum, respectively. 

Section 2.4 describes key discussion points raised during work group deliberations concerning 

the use of NOCTS as a substitute for obtaining and evaluating the full worker population. 

2.1 ORAUT-OTIB-0075, “Use of Claimant Datasets for Coworker Modeling” 

In SC&A’s opinion, the first substantive treatment of the subject was NIOSH’s report, ORAUTOTIB-0075, “Use of Claimant Datasets for Coworker Modeling.” NIOSH issued revision 00 on 

May 25, 2009 (NIOSH, 2009), and revision 01 on June 17, 2016 (NIOSH, 2016). It presented 

“the results of a study of Y-12 Plant worker and claimant data to determine the feasibility of 

using claimant data in place of complete coworker data for reconstruction of doses at sites that 

do not have complete coworker data [in an electronic database]” (NIOSH, 2009, p. 2). This 

report also included Mound and SRS datasets as a supportive basis for using NOCTS monitoring 

records in sitewide co-exposure development. 
SC&A, Inc.

Application of NOCTS Data, page 2 July 29, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

SC&A reviewed revision 00 of OTIB-0075 and provided comments in a January 13, 2010, white 

paper (SC&A, 2010). SC&A’s overall conclusions were divided into two issues: 

1. whether the hypothesis that NOCTS data are representative of all worker data can be 

proven 

2. whether the claimant database as compiled from NOCTS provides a satisfactory basis for 

a co-exposure model for construction trade workers (CTWs) at SRS such that it would 

meet the requirements of dose reconstruction with sufficient accuracy 

For OTIB-0075 issue 1, it is important to note that “representative” in the context of OTIB-0075 

simply refers to whether the derived distribution and parameter estimates for the two groups 

(NOCTS and all worker) are statistically similar. “Representative” in the OTIB-0075 context 

does not refer to the extent to which diverse worker types, monitoring protocols, and associated 

exposure potential (i.e., strata) are appropriately captured in the NOCTS dataset.

On the first issue, SC&A found the following: 

1. The uranium dataset for the Y-12 National Security Complex (Y-12) conforms to the 

OTIB-0075 hypothesis of claimant data representativeness. 

2. The data for Mound indicate significant differences between claimant and all-worker 

plutonium bioassay data.1

 

1

 This issue was addressed in a subsequent revision of OTIB-0075 with the evaluation of additional claimant data 

coded by NIOSH, as discussed later in this section.

3. The SRS tritium data cover a very narrow period from 1990 to 2001. These data show no 

significant differences at the annual level of aggregation, but the sample size is very 

small, and the regression results were dominated by a single year with high exposure, 

1991. 

In summary, SC&A (2010) found in its review of OTIB-0075 that it appears NOCTS can be 

considered statistically similar at the aggregate level to the full worker population in these 

specific instances, but only for uranium urinalysis at Y-12 (1950–1988), plutonium urinalysis at 

Mound, and tritium dose at SRS (1991–2000). 

Specific to SRS, SC&A’s (2010) review of OTIB-0075, revision 00, found that a conclusion that 

the SRS claimant data from the 1990s for tritium are representative of the overall claimant 

population can, at best, be applied to that radionuclide and that period, but that conclusion cannot 

be back-extrapolated to other periods. Even within the period in question, there are differences 

between construction workers disaggregated by craft and non-construction workers. SC&A also 

found that there are considerable differences in exposures between job types and areas, and the 

data indicate that construction workers in some areas and periods had greater exposure potential 

than all non-construction workers. 
SC&A, Inc.

Application of NOCTS Data, page 3 July 29, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

In 2017, SC&A performed a focused review of revision 01 of OTIB-0075 to address the extent 

to which the revision addressed these concerns (SC&A, 2017). However, the primary revisions 

to OTIB-0075 were the incorporation of the time-weighted, one-person one-sample method for 

evaluating bioassay data and an updated lists of claimants and claimant data that expanded the 

available dataset for statistical analysis. Notably, the expansion of the Mound plutonium data in 

revision 01 addressed SC&A’s concerns about observed differences between the claimant and 

all-worker populations for plutonium (SC&A, 2017). However, SC&A found that revision 01 of 

OTIB-0075 did little to address SC&A’s main concerns about adequate and complete 

representation of exposures among the claimant population when compared to the full worker 

population. 

2.2 ORAUT-OTIB-0081, “Internal Dosimetry Co-exposure Data for the Savannah River Site” 

On February 8, 2013, NIOSH issued ORAUT-OTIB-0081, revision 00, which has since been 

revised a number of times up to revision 05, issued on September 1, 2020 (NIOSH, 2020a). 

Bioassay data in the NOCTS dataset for SRS employees were used to develop what was intended 

to be a representative database of co-exposure bioassay data using the guidance of OTIB-0075, 

revision 01 (NIOSH, 2016), supplemented by original data from laboratory logbooks 

(i.e., non-claimant data) for the trivalent actinides, thorium, and neptunium. The additional 

laboratory logbook data were compiled due to inadequate data for those radionuclides in the 

claimant population. For the period before availability of the Health Protection Radiation 

Exposure Database data (before 1991) at SRS, NOCTS data were used in lieu of capturing and 

coding the full site dataset for a number of the remaining pertinent radionuclides (e.g., 

plutonium, uranium, fission products, tritium). While the NOCTS compilation is not a complete 

set of SRS worker data, OTIB-0081 (i.e., the SRS co-exposure model) notes that NOCTS was 

“the best available compilation of data in a usable form (i.e., electronic spreadsheet or database)” 

(NIOSH, 2020a, p. 28). 

From its analysis for the three evaluated cases in OTIB-0075, NIOSH concluded that claimant 

datasets can be considered to be random samples of the complete site dataset and that this 

justifies applying this assumption to other sites and datasets. Thus, NIOSH assumed the NOCTS 

data to be close enough to a random sampling that they can be considered representative of 

co-exposure bioassay data for the full SRS site based on the example analyses in OTIB-0075. In 

its review of OTIB-0081, revision 04, SC&A (2019) describes several open findings related to 

OTIB-0075 in the focused context of the co-exposure model. Specifically, SC&A (2019, p. 75) 

notes: 

Issues associated with the representativeness of claimant datasets to the sitewide 

worker population is beyond the scope of this report and thus should be addressed 

separately.

2.3 ORAUT-RPRT-0094, “Bioassay for Subcontractor Trade Workers at the Savannah River 

Site” 

ORAUT-RPRT-0094, revision 00, was issued on September 13, 2019 (NIOSH, 2019b). This 

report provides estimates of the numbers and fractions of subcontractor construction trade 

workers (subCTWs) identified in NOCTS who were monitored by SRS for external and internal 

exposure during 1972 through 1997. These estimates were established from the number of claims 
SC&A, Inc.

Application of NOCTS Data, page 4 July 29, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

in the NOCTS database in which one or more position descriptions met the definition of a CTW 

and then through a manual review of SRS dosimetry documents in which those claimants had 

records of external monitoring, whole-body counts, and urine bioassay results within each year. 

SC&A’s March 8, 2021, review of RPRT-0094 (SC&A, 2021) found that while a considerable 

amount of NOCTS data cover the timeframe and facilities in question, the RPRT-0094 analysis 

suffers from two basic flaws:

1. It homogenizes all forms of SRS internal monitoring data into a single metric for 

application, which precludes a definitive treatment of data completeness for specific 

radionuclide source terms. 

2. More fundamentally, it does not substantiate the actual representativeness of the 

claimant data sample collected as compared to that of the overall site worker population.

At the subsequent March 23, 2021, meeting of the joint SRS and SEC Issues work groups, 

NIOSH presented a subset of the NOCTS internal monitoring dataset that focused specifically on 

plutonium bioassay data. NIOSH found for plutonium that for 1990–1998, a high percentage of 

subCTWs (>75 percent) in NOCTS were monitored and would be sufficiently represented in a 

co-exposure model. For 1980–1989, a moderate percentage (>50 percent) of subCTWs in 

NOCTS were monitored. For 1972–1979, initially a moderate percentage of subCTWs were 

monitored for internal exposures, with a marked decrease into the late 1970s followed by a surge 

of monitoring starting in 1980 (NIOSH, 2021c). NIOSH’s overall conclusion was that the trend 

observed in these data is that the subCTWs who were monitored were represented as least as 

well as other SRS workers and that the completeness of the data is more than adequate for dose 

reconstruction and for the basis of the SRS co-exposure model (NIOSH, 2021c). 

SC&A’s view is that data representativeness in this context is different from whether 

subcontractors are “represented” as well as other worker categories. In SC&A’s view, data 

representativeness is more aligned with how “representativeness” is defined in the co-exposure 

guideline, DCAS-IG-006, revision 00, “Criteria for the Evaluation and Use of Co-Exposure 

Datasets” (NIOSH, 2020c; IG-006). Specifically, IG-006 states that a given co-exposure model 

should “be established from monitored workers with comparable activities and relationships to 

the radiation environment. . . . [and] ensure that it is either representative of the distribution of 

exposures for the intended population or that it provides a plausible upper bound for those 

workers” (emphasis added) (NIOSH, 2020c, pp. 4–5). 

2.4 Summary of prior work group discussion points

SRS and SEC work group discussions about application of the NOCTS dataset focused primarily 

on the three previously discussed NIOSH reports. The following list summarizes pertinent 

comments by NIOSH, SC&A, and the work group members: 

• SC&A commented that notwithstanding the high percentage of monitored subcontractors 

reported for NOCTS, the key question is “monitored for what?” Were they monitored for 

the correct radionuclide based on the job-specific work to which they were assigned? 

SC&A pointed out that the original intent of ORAUT-RPRT-0092 (NIOSH, 2019a) was 

to determine if subcontractors were monitored similar to other SRS workers and not 
SC&A, Inc.

Application of NOCTS Data, page 5 July 29, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

simply whether they had any bioassay (ABRWH, 2020, p. 98). NIOSH acknowledged 

that coworker comparisons in relation to the work environment are not feasible with the 

NOCTS dataset and “therefore the data completeness really must be inferred” (ABRWH, 

2019, p. 216). 

• Work group members questioned the representativeness of the NOCTS dataset, as 

compared with the general site worker population, given that it consists of claimants who 

have some compensable form of cancer under the Energy Employees Occupational 

Illness Compensation Program Act. NIOSH responded that “these are the people with 

cancer and so they are the ones who might have been harmed from that standpoint, 

therefore did they have any exposure and do they have monitoring data?” (ABRWH, 

2019, p. 219). However, work group members noted that they were unaware of any 

literature that linked people who had contracted cancer as being representative of larger 

populations and that “the criteria” (i.e., IG-006) prescribes representation from the 

workforce rather than a subsegment of the workforce (ABRWH, 2019, pp. 219–220). 

Similar brief discussions of the joint SRS and SEC Issues work groups concerning the 

assumed exposure potential of the claimant population versus the full site population 

occurred during the March 2021 teleconference (ABRWH, 2021a, pp. 29, 91–93) and 

continued during the full Advisory Board on Radiation and Worker Health (ABRWH, 

Board) meeting in April 2021 (ABRWH, 2021b, pp. 57, 65, 86–89). However, the issue 

was not resolved during those discussions. 

• For NOCTS as a measure of completeness, NIOSH cites the high percentage of 

subcontractors with internal monitoring data for SRS in NOCTS (e.g., 89 percent with 

any form of internal monitoring in 1990 (NIOSH, 2020b, p. 44)) but, at the same time, 

acknowledges that:

There is a potential detriment. We can't directly compare coworkers, 

therefore the data completeness really must be inferred . . . . We can look 

at subcontractors, but we can't look at this subcontractor, were they paired 

with another subcontractor on the RWP. We can't do that. [ABRWH, 

2019, p. 216] 

SC&A commented that while a NOCTS-based approach does offer some advantages in 

its simplicity, timeliness, and resource efficiency, SC&A continues to conclude that it 

does not meet the intent of IG-006 that data completeness be determined from sufficient 

measurements “established from monitored workers with comparable activities and 

relationships to the radiation environment” (NIOSH, 2020c, p. 4). 

• SC&A notes that the co-exposure guideline (IG-006) provides for use of claimant 

information as a “useful starting point . . . to look at the distribution of samples among 

the various categories of workers represented in the claimant population at the site,” with 

the illustrative example in that guidance being workers monitored for plutonium-239 at 

the Nevada Test Site (NIOSH, 2020c, p. 6). However, SC&A believes the actual intent of 

this example is to have NOCTS as a backup means to validate or check whether the 

“right people [worker categories] were monitored” (ABRWH, 2014, p. 26), not as 
SC&A, Inc.

Application of NOCTS Data, page 6 July 29, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

guidance for wholesale substitution of NOCTS data for pertinent site-specific information 

and datasets to support co-exposure models. 

• SC&A further notes that although IG-006 does discuss the use of claimant data as a 

potential source to verify the completeness of electronic datasets intended to reflect the 

full monitored site population, it does not indicate these comparative analyses would 

provide adequate basis for substitution of the claimant data in lieu of obtaining and using 

the monitoring records for the full site population. The specific language used in IG-006 

is as follows: “if electronic records or summary databases are used to develop the 

co-exposure model, these should be reviewed against a representative sampling of 

original data where possible to verify that they contain a complete and unbiased listing of 

all the data collected at the site” (NIOSH, 2020c, p. 8). As such, IG-006 recommends 

using NOCTS to validate available site-specific data, not to replace site-specific data.

The issue of applying NOCTS bioassay data came up in other work group discussions, but the 

preceding list represents key points relevant to the question of broader application of NOCTS 

bioassay datasets to support co-exposure models where readily available site-specific electronic 

dosimetry records are unavailable or incomplete (i.e., the electronic records do not contain all of 

the available monitoring results).

3.0 Overall Status and Conclusions

From the assessments and proceedings discussed in the previous three sections, SC&A concludes 

that NOCTS does have utility as supplementary evidence of who was monitored, as well as a 

means to validate site-specific electronic databases intended to represent the full monitored 

population. However, SC&A did not find sufficient past evidence that NOCTS has been 

approved by the Board to be applied as a wholesale substitution of the full monitored worker 

population at a site without evidence of its representativeness in relation to those workers. If a 

particular site can be shown to have sufficiently complete electronic datasets, the NOCTS dataset 

for that site can be compared with site data to validate its representativeness, therefore permitting 

its sitewide use for the time periods and facilities covered (as was done for uranium at Y-12 in 

OTIB-0075). 

Conversely, if site monitoring practices or recordkeeping can be shown to have potential gaps, 

the corresponding completeness and/or representativeness of the available data in any form 

(whether hardcopy, NOCTS, or electronic datasets) would be questionable. The ultimate 

question is whether one can balance the available weight of evidence of a site’s monitoring 

adequacy and data completeness with the availability and representativeness of NOCTS data to 

arrive at a judgment supporting its application under IG-006 guidelines. Fundamentally, such an 

assessment cannot be performed in isolation of the historical monitoring program conducted at 

the site; it is not enough to infer data completeness by a review of NOCTS alone. 

SC&A recommends that further evaluation of NOCTS and its merits as a basis for broader site 

application in developing co-exposure models is not warranted until the Board resolves the 

fundamental policy question of whether a universal programmatic assumption concerning 

representativeness of the claimant population can ever be sufficiently validated across all sites of 

intended application. 
SC&A, Inc.

Application of NOCTS Data, page 7 July 29, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

4.0 References

Advisory Board on Radiation and Worker Health. (2014). SEC Issues Work Group Tuesday 

October 28, 2014 [Transcript of teleconference meeting].

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2014/wgtr102814.pdf 

Advisory Board on Radiation and Worker Health. (2019). Savannah River Site (SRS) and SEC 

Issues Work Groups joint meeting Thursday, December 5, 2019 [Transcript].

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2019/wgtr120519-508.pdf 

Advisory Board on Radiation and Worker Health. (2020). Joint meeting of the Savannah River 

Site (SRS) and Special Exposure Cohort (SEC) Issues Work Groups Thursday, November 17, 

2020 [Transcript of teleconference meeting].

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2020/wgtr111720-508.pdf 

Advisory Board on Radiation and Worker Health. (2021a). Savannah River Site (SRS) and SEC 

Issues Work Groups joint meeting Tuesday, March 23, 2021 [Transcript of teleconference 

meeting]. https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2021/wgtr032321-508.pdf 

Advisory Board on Radiation and Worker Health. (2021b). Advisory Board on Radiation and 

Worker Health 139th meeting Thursday, April 15, 2021 [Transcript of teleconference meeting]. 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2021/tr041521-508.pdf 

National Institute for Occupational Safety and Health. (2009). Use of claimant datasets for 

coworker modeling (ORAUT-OTIB-0075, rev. 00). 

https://www.cdc.gov/niosh/ocas/pdfs/arch/tibs/or-t75-r0.pdf 

National Institute for Occupational Safety and Health. (2016). Use of claimant datasets for 

coworker modeling (ORAUT-OTIB-0075, rev. 01). https://www.cdc.gov/niosh/ocas/pdfs/tibs/ort75-r1.pdf 

National Institute for Occupational Safety and Health. (2019a). Evaluation of bioassay data for 

subcontracted construction trade workers at the Savannah River Site (ORAUT-RPRT-0092, 

rev. 00). https://www.cdc.gov/niosh/ocas/pdfs/orau/oraurpts/or-rprt-92-r0-508.pdf 

National Institute for Occupational Safety and Health. (2019b). Bioassay for subcontractor 

construction trade workers at the Savannah River Site from 1972 to 1997 (ORAUT-RPRT-0094, 

rev. 00). https://www.cdc.gov/niosh/ocas/pdfs/orau/oraurpts/or-rprt-94-r0-508.pdf 

National Institute for Occupational Safety and Health. (2020a). Internal dosimetry co-exposure 

data for the Savannah River Site (ORAUT-OTIB-0081, rev. 05). 

https://www.cdc.gov/niosh/ocas/pdfs/tibs/or-t81-r5-508.pdf 

National Institute for Occupational Safety and Health. (2020b, November 17). Response to 

SC&A comments on ORAUT-RPRT-0092 [Presentation to the Savannah River Site Work Group].

https://ftp.cdc.gov/pub/FOIAREQ/183714_red-508.pdf 
SC&A, Inc.

Application of NOCTS Data, page 8 July 29, 2021

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 

National Institute for Occupational Safety and Health. (2020c). Criteria for the evaluation and 

use of co-exposure datasets (DCAS-IG-006, rev. 00). 

https://www.cdc.gov/niosh/ocas/pdfs/dr/dc-ig-006-r0-508.pdf 

National Institute for Occupational Safety and Health. (2021a). Analysis of uncertainty in 

co-exposure models [White paper]. https://ftp.cdc.gov/pub/FOIAREQ/184480-508.pdf 

National Institute for Occupational Safety and Health. (2021b). Practical implications of the 

bootstrap uncertainty analyses on co-exposure models [White paper]. 

https://ftp.cdc.gov/pub/FOIAREQ/184554-508.pdf 

National Institute for Occupational Safety and Health. (2021c, March 23). Bioassay for 

subcontractor construction trade workers at the Savannah River Site from 1972 to 1997

[Presentation to the Savannah River Site Work Group]. 

https://ftp.cdc.gov/pub/FOIAREQ/184935-508.pdf 

SC&A, Inc. (2010). Review of ORAUT-OTIB-0075: Use of claimant datasets for coworker 

modeling for construction workers at Savannah River Site [White paper]. 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-ortib75-r0.pdf 

SC&A, Inc. (2017). SC&A’s evaluation of ORAUT-OTIB-0075, revision 01, “Use of claimant 

datasets for coworker modeling” (SCA-TR-2017-PR011, rev. 0). 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-ortib75r1-r0.pdf 

SC&A, Inc. (2019). Review of ORAUT-OTIB-0081, revision 04, “Internal coworker dosimetry 

data for the Savannah River Site” (SCA-TR-2019-SEC004, rev. 0). 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/178392_red-508.pdf 

SC&A, Inc. (2021). Summary of key issues concerning internal monitoring completeness and 

representativeness for SRS subcontractor construction trade workers (SCA-TR-2021-SEC002, 

rev. 0). https://ftp.cdc.gov/pub/FOIAREQ/185250-508.pdf